249
Chapter 9
Timer / Counter (Real Time Pulse Unit)
Preliminary User’s Manual U14913EE1V0UM00
(1)
Timers D Registers 0, 1 (TMD0, TMD1)
TMDn is a 16-bit timer. It is mainly used as an interval timer for software (n = 0, 1).
Starting and stopping TMDn is controlled by the CE bit of the timer D control register n (TMCDn).
A division by the prescaler can be selected for the count clock from among f
CPU
/2, f
CPU
/4, f
CPU
/8,
f
CPU
/16, f
CPU
/32, f
CPU
/64, f
CPU
/128, and f
CPU
/256 by the CS2 to CS0 bits of the TMCDn register.
TMDn is read-only in 16-bit units.
Figure 9-2: Timer D Registers 0, 1 (TMD0, TMD1)
The conditions for which the TMDn register becomes 0000H are shown below.
• Reset input
• CAE bit = 0
• CE bit = 0
• Match of TMDn register and CMDn register
• Overflow
Cautions: 1. If the CAE bit of the TMCDn register is cleared (0), a reset is performed asynchro-
nously.
2. If the CE bit of the TMCDn register is cleared (0), a reset is performed, synchro-
nized with the internal clock. Similarly, a synchronized reset is performed after a
match with the CMDn register and after an overflow.
3. The count clock must not be changed during a timer operation. If it is to be over-
written, it should be overwritten after the CE bit is cleared (0).
4. Up to f
CPU
/2 clocks are required after a value is set in the CE bit until the set value
is transferred to internal units. When a count operation begins, the count cycle
from 0000H to 0001H differs from subsequent count cycles.
5. After a compare match is generated, the timer is cleared at the next count clock.
Therefore, if the division ratio is large, the timer value may not be zero even if the
timer value is read immediately after a match interrupt is generated.
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Address
Initial
value
TMD0
FFFFF540H 0000H
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Address
Initial
value
TMD1
FFFFF550H 0000H
Содержание V850E/CA1 ATOMIC
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